How to Use Static Methods and Variables in Kotlin?

How can I implement static methods and variables in Kotlin?

// Example of using Companion Object in Kotlin
class Foo private constructor() {
    companion object {
        private var instance: Foo? = null

        fun getInstance(): Foo {
            if (instance == null) {
                instance = Foo()
            }
            return instance!!
        }
    }
}

In Kotlin, static methods and variables are handled differently due to the absence of static members in classes. Instead, Kotlin uses 'companion objects' to achieve similar functionality. This structure allows you to create methods and variables that are associated with the class rather than instances of the class, enabling singleton patterns and similar use cases.

class Foo private constructor() {
    companion object {
        private var instance: Foo? = null

        fun getInstance(): Foo {
            if (instance == null) {
                instance = Foo()
            }
            return instance!!
        }
    }
}

Causes

• Kotlin does not support static members natively like Java.
• To create class-level properties and methods, use companion objects.

Solutions

• Define a companion object within your class for static-like behavior.
• Use `private constructor` to restrict instance creation, enabling singleton implementation.

Mistake: Attempting to use `static` keyword for methods or variables.

Solution: Use companion objects instead for defining class-level variables and methods.

Mistake: Forgetting to handle the instance variable for null checks appropriately.

Solution: Implement null checks properly within the `companion object` to ensure safe instance retrieval.